My dad (and i won't be defeated) has challeneged me to find the one word in the english language that contains three sets of alphabetically consecutive letter pairs. I.e. ab or jk. Does anyone have a clue?

one word?? according to whose dictionary?

well, fwiw, here's a clue:
plug de*no*st into OneLook
or try: abst* and peruse the results (or ab*st - this one reveals a six-letter word!)

To be honest I hadn't done much research myself. Thanks for the tip though. I will have words with my dad

I suppose abstentionist doesn't count because the st pair is used twice. Presumably you mean three unique pairs of alphabetically consecutive letters.

won't be defeated

You might want to define your terms, too. If they don't have to be in alphabetical order, if a letter can be in two runs and they don't have to be three different pairs defeated qualifies. In fact it has four pairs.

defeated
defeated
defeated
defeated

But, I suppose, if he insists it's unique.

Maybe if we hired some ghostwriters they could find the word for us. And if they are successful it would be demonstrably delightable. (Rather obsolete I admit. We should probably abstrude "delightable" from the search. After all, if we came up with too many words [thanks to the OneLook dictionary] it might destabilize your relationship with your father, which would be understandably detestable.)